The present invention relates to a medium transporting device that transports a medium and a recording apparatus incorporating the medium transporting device.
A printer, one type of recording apparatus, is equipped with a medium transporting device including a drive roller and a follower roller that together pinch and transport a sheet of paper used as a recording medium to a recording section, and a ejection roller and a spur that together pinch and transport the sheet of paper to a discharge portion. The medium transporting device is provided with a detector to detect a quantity of rotations of the drive roller, and a quantity of rotations of the drive roller is controlled by feeding back a detection signal from the detector (see Japanese Patent Publication No. 7-304222A). Another medium transporting device is provided with a reader to optically read a test pattern that has been provided previously on a sheet of paper, and transportation of a sheet of paper is controlled by calculating a correction value for a quantity of transportation of the sheet of paper on the basis of a read signal from the reader (see Japanese Patent Publication No. 2002-273956A).
The former medium transporting device, however, is not able to control transportation errors occurring beyond the detector, that is, eccentric errors of the drive roller, errors of the diameter of the drive roller, slipping errors between the drive roller and a sheet of paper, etc. In addition, once the trailing end of a sheet of paper is released from pinching between the drive roller and the follower roller, the sheet of paper is transported by being pinched between the ejection roller and the spur alone. Transportation control by the detector is thus no longer performed, which may possibly deteriorate transportation accuracy of a sheet of paper. Further, a detection roller, serving as the detector, is supported by radial bearings provided with circular holes, and is therefore not able to suppress torsional vibrations, which may possibly adversely affect transportation of a sheet of paper. Meanwhile, the latter medium transporting device is able to calculate a correction value only when a sheet of paper provided with the test pattern is transported, and this value is effective in a short region for merely a limited kind of sheet of paper.